News & Articles on Household-Size (Small) Wind Turbines

French Offshore VAWT Developer Nénuphar Goes Bust

The French offshore Vertical-Axis Wind Turbine developer Nénuphar closed its doors in early 2018. Their web site is dark, though there are several Nenuphar Animations on YouTube.com.

Named after the European water lily (Nymphaea alba), the company based in Lille in northern France built several prototypes under the name Vertiwind before pulling up stakes.

The company failed after French nuclear plant constructor Areva and French state-owned utility Électricité de France refused to fund further development. At the time Areva itself was facing financial problems and has since been restructured with its reactor business absorbed by EDF.

Investment by electric utilities has usually been the "kiss-of-death" for wind turbine start-ups. And it proved true again in this case.

The French government pumped at least €7 million into Nénuphar. (See Ademe's promotional flyer on the project.)

Nénuphar said in 2012 that it would have 25 MW in 13 floating offshore turbines by 2015.

As late as mid 2014 Nénuphar was claiming it could build a multimegawatt offshore turbine for one-third less than conventional turbines.

This was quite a leap from the 35 kW prototype of a fairly standard straight-bladed VAWT in 2009. The rotor on the prototype was cluttered with struts and stays, a lesson apparently not learned from other failed H-rotor projects that preceded Nénuphar.

In 2015 the company claimed that their 2 MW prototype was the largest on-shore VAWT in the world. While no doubt true at the time, it wasn't the largest VAWT ever built. That title goes to Canada's Eole, a 4 MW giant with a swept area of 4,000 m². Eole operated from 1987 to 1993 and generated 12 million kWh.

Without access to details from the defunct developer, it's difficult to tell exactly what they accomplished with the on-shore prototype. Reportedly, the prototype was 50 m in diameter with blades 25 m in length, giving the rotor 1,250 m² of swept area. It's hard to imagine that Nénuphar rated this prototype at 2 MW and expected people to believe it. Then proceeded to raise the rated power to 2.6 MW. This is excessive even for VAWTs that have been notoriously overrated.

It has since been brought to my attention that the second prototype was not rated at 2 MW.

Modern IEC Class I on-shore turbines for very windy locations will have specific capacity of 300-400 W/m² and specific area of 2.5-3 m²/kW. Turbines designed for low wind sites will have specific areas twice these values.

For those new to wind energy, what makes a wind turbine cost effective is how much electricity--in kWh--a wind turbine generates relative to its total cost. High power ratings or low specific areas do not directly correspond to the amount of electricity a wind turbine will generate and thus are only indirectly related to cost effectiveness even in very windy locations.